Self-drilling differential grouting combined bolt and anchoring method therefor

ABSTRACT

A self-drilling differential grouting combined bolt, as described consists essentially of a drill (1), a grouting pipe (2), a spindle (3), a bolt head mechanism and a bolt tail mechanism, wherein the bolt head mechanism comprises a fixed ring (4), a slip ring (7), a limiting pipe (6) and several pairs of driven linkages (501) and driving linkages (502); and the bolt tail mechanism comprises a bolt disc (11), a connecting cap (12), a spring (13) and a nut (14), the bolt disc (11) is sleeved on a rear end of the grouting pipe (2), the connecting cap (12) is passed through by the spindle (3) and blocks off the rear end of the grouting pipe (2), the connecting cap (12) is provided with a grouting hole in communication with the grouting channel in the grouting pipe (2), and a grouting hole and an air vent are provided in the bolt disc (11).

BACKGROUND Technical Field

The present invention relates to a supporting member and its supportingmethod for soft and fractured rocks, in particular to a self-drillingdifferential grouting composite rock bolt and an anchoring method.

Related Technology

The support of weak and fractured surrounding rock is one of the keyissues in the field of stability control of geotechnical engineering. Atpresent, the common effective treatment method for this kind ofsurrounding rock is to first reinforce the fractured surrounding rock bygrouting, and then to support the grouted surrounding rock by adoptingrock bolts, anchor cables, etc.

The grouting process is usually realized by conventional grouting rockbolts or self-drilling grouting rock bolts. The conventional groutingrock bolt has the advantages of simple structure, easiness in processingand low cost, but it is not easy for the conventional grouting rock boltto enter the bolting hole because of the hole collapse, and it needs tobe fixed and sealed specially, which is lengthy and not conducive torapid installation. The self-drilling grouting rock bolt avoids theinfluence of hole collapse, but it still needs to be fixed and sealedbefore grouting.

The key problem of current combined support with grouting and bolting isthat the grouting reinforcement and the installation of rebar rock boltare often carried out in two steps. On the one hand, the drillingworkload is very high and time-consuming, which not only leads to theslow construction speed, but also greatly increases the engineeringcost. On the other hand, there is no strong coupling between thegrouting rock bolt and the rebar rock bolt, consequently the synergisticanchoring effect is weak, and the anchoring performance and reliabilityof the support system are low.

In order to overcome the above-mentioned defects of the existingcombined support technology with grouting and bolting, it is necessaryto develop a composite rock bolt which combines the functions andadvantages of the grouting rock bolt and the high-strength rebar rockbolt.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the defects of theprior support technology, provide a self-drilling differential groutingcomposite rock bolt and an anchoring method thereof. Under the conditionof improving the supporting effect, the supporting process of weak andfractured surrounding rock is sped up and the engineering cost isreduced.

The present invention provides a self-drilling differential groutingcomposite rock bolt, consisting of a drill bit, a grouting pipe, a mainshaft, an anchor head assembly and an anchor tail assembly.

The drill bit is connected to the front end of the main shaft, thegrouting pipe is sleeved over the main shaft. The inner diameter of thegrouting pipe is greater than the diameter of the main shaft, so agrouting passage is formed between the grouting pipe and the main shaft.

The anchor head assembly includes a sliding ring, a limiting pipe, and aplurality of pairs of driven connecting rods and driving connectingrods. The sliding ring is sleeved over the main shaft and connected tothe front end of the grouting pipe (the end at which the drill bit islocated is the front end). The limiting pipe is sleeved over the mainshaft and located between the drill bit and the sliding ring; thelimiting pipe is shorter than the total length of one pair of drivingand driven connecting rods; the limiting pipe is provided with somegrouting holes. The driven connecting rods are uniformly distributed inthe circumferential direction and hinged to the front end of the mainshaft; the driving connecting rods are uniformly distributed in thecircumferential direction and hinged to the sliding ring; the drivenconnecting rods and the driving connecting rods are hinged in pairs.

The anchor tail assembly includes an anchor plate and a connecting nut,the anchor plate is sleeved over the rear end of the grouting pipe, andthe connecting nut is sleeved over the main shaft and blocks the rearend of the grouting pipe. The connecting nut is provided with a groutinghole connected with the inner space of the grouting pipe. The anchorplate is also provided with a grouting hole.

The further optimized schemes of the present invention are as follows.

Optimized scheme 1: The anchor head assembly further includes a fixedring, and the fixed ring is fixed at the front end of the main shaft.Each driven connecting rod is hinged to the fixed ring, and the frontend of the limiting pipe is fixed on the fixed ring.

Optimized scheme 2: When the driven connecting rods are at a positionparallel to the main shaft, the inner side of each driven connecting rodis in contact with the outer surface of the limiting pipe, and theradius of the circle formed by hinging points on the sliding ring issmaller than the radius of the circle formed by hinging points on thefixed ring, thereby guaranteeing that three hinging points of each pairof driving connecting rod and driven connecting rod are always notco-linear.

Optimized scheme 3: A foldable connecting rod unit is provided betweenadjacent driving connecting rods, and a grout stop screen is providedbetween each foldable connecting rod unit and the sliding ring.

Optimized scheme 4: The foldable connecting rod unit consists of twobrace rods and a ratchet box; the two brace rods are connected at oneend by the ratchet box, and hinged at the other end to two adjacentdriving connecting rods.

Optimized scheme 5: The inner wall of the sliding ring is provided withgrooves in axial direction, through which grout can enter the limitingpipe from the grouting pipe.

Optimized scheme 6: A spring is sleeved over the connecting nut; next tothe connecting nut is a locknut whose outer end is provided with alocking ring capable of preventing the nut from being loosened. Thespring enables the rock bolt to act in time and stay in an activesupporting state for a long time.

Optimized scheme 7: A grout stop plug is sleeved over the outer part ofthe grouting pipe, and one grouting hole and one exhaust hole aredrilled at two positions of both the grout stop plug and the anchorplate.

Optimized scheme 8: Each of the grouting pipe and the main shaft isintegral or formed by a plurality of pipes (shafts) connected by usingconnecting sleeves.

By using the composite rock bolt provided by the present invention, holedrilling, hole expanding at the inner anchor end and differentialgrouting (fracture grouting is performed at the inner anchor end throughthe gap between the grouting pipe and the main shaft, and permeationgrouting is performed at the other sections through the gap between thegrouting pipe and the bolting hole), and timely active supporting can beperformed in weak and fractured surrounding rock. The grouting pipeanchors the surrounding rock in a small range by full-length anchorage;the main shaft squeezes and reinforces the surrounding rock in a largerange including the grouting pipe anchorage zone; the grouting pipeanchorage zone and the main shaft anchorage zone interact with eachother and cooperatively bear the load, such that the supporting effectcan be effectively improved.

A method for anchoring the self-drilling differential grouting compositerock bolt includes the following steps:

step 1: hole drilling: removing the spring and nut of the composite rockbolt, adjusting the connecting nut to make driven connecting rods to beparallel to the main shaft, using a bolter to rotate the composite rockbolt to drill a bolting hole with preset depth;

step 2: hole expanding at inner anchor end: gradually adjusting theconnecting nut to enable the grouting pipe to push the sliding ring tothe bottom of the hole such that driving connecting rods push the drivenconnecting rods to protrude in the radial direction, at the same time,using the bolter to rotate the rock bolt to enable the hole diameter ofthe inner anchor end (the end at which the rock bolt enters the boltinghole is called the inner anchor end, also known as the front end of therock bolt, and the other end of the rock bolt is called the outer anchorend, also known as the rear end) to be gradually expanded, andcompleting the hole expanding of the inner anchor end when the slidingring is stopped by the limiting pipe;

step 3: differential grouting: first connecting the grouting pipelinewith the grouting hole of the connecting nut, performing fracturegrouting to rocks around the inner anchor end through the internal partof the grouting pipe by adopting high grouting pressure, then connectingthe grouting pipeline with the grouting hole of the anchor plate, andperforming permeation grouting to rocks around the grouting pipe throughthe gap between the grouting pipe and the bolting hole;

step 4: rock bolt fastening: after grout is initially solidified,mounting the spring and the locknut at the outer anchor end, andapplying a certain pre-tightening force to the surrounding rock by usingthe locknut to compress the spring to produce a certain amount ofcompression.

The present invention has the following beneficial effects.

(1) The present invention combines the grouting pipe and thehigh-strength main shaft to simultaneously provide the functions ofgrouting and high-strength anchoring. It can not only improve thesupporting effect, but also reduce the number of bolting holes.Consequently, it can save construction time supporting cost.

(2) The self-drilling function of the rock bolt avoids the bad influenceof hole collapse on the installation of the rock bolt; the compositerock bolt is easy to assemble; the rock bolt with appropriate size andmechanical parameters can be designed according to specific rockcharacteristics and stress conditions.

(3) The large-diameter anchor head and the large-scale reinforcementzone of fracture grouting ensure that the inner anchoring point is firm,stable and reliable.

(4) The spring at the outer anchor end not only enables the rock bolt toact in time and stay in an active supporting state for a long time, butalso plays a certain role of resisting impact. These features guaranteegood supporting effect and adaptability.

(5) Differential grouting takes account of both reinforcement andyielding to obtain good anchoring effect. The fracture grouting at theinner anchor end can connect the internal anchoring points of adjacentrock bolts into a whole body to ensure the stabilization of the inneranchor end; while the permeation grouting at the other parts can leavesome unconsolidated surrounding rock between adjacent rock bolts toprovide a compressive deformation space and play the role of yielding.

(6) The small-range anchorage zone formed by the grouting pipe whichacts as a full-length bonded rock bolt and the large-scale anchoragezone controlled by the main shaft which acts as a high-strength rockbolt interact cooperatively with each other to bear the load, such thatthe supporting effect can be greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a structural schematic view of a self-drilling differentialgrouting composite rock bolt provided by the present invention(longitudinal sectional view, in which driven connecting rods areparallel to a main shaft).

FIG. 2 is a structural schematic view of the self-drilling differentialgrouting composite rock bolt provided by the present invention(longitudinal sectional view, in which an anchor head assembly are in anexpanded state).

FIG. 3 is a structural schematic view of the self-drilling differentialgrouting composite rock bolt provided by the present invention(longitudinal sectional view, in which the anchor head assembly are inan expanded state and springs and nuts are installed at the outer anchorend).

FIG. 4 is a schematic view of a self-drilling differential groutingcomposite rock bolt provided by the present invention when a grout stopscreen is opened.

FIG. 5 is a schematic view of a foldable connecting rod unit when thefoldable connecting rod unit is folded.

FIG. 6 is a schematic view of a foldable connecting rod unit when thefoldable connecting rod unit is unfolded.

FIG. 7 is a schematic view of a self-drilling differential groutingcomposite rock bolt provided by the present invention when hole drillingis completed.

FIG. 8 is a schematic view of a self-drilling differential groutingcomposite rock bolt provided by the present invention after holeexpanding at the inner anchor end.

FIG. 9 is a schematic view of a self-drilling differential groutingcomposite rock bolt provided by the present invention after differentialgrouting.

FIG. 10 is a schematic view of a self-drilling differential groutingcomposite rock bolt provided by the present invention after fastening.

DETAILED DESCRIPTION

The present invention will be further described below in combinationwith the accompanying drawings and the embodiments.

As illustrated in FIGS. 1-3, the present invention provides aself-drilling differential grouting composite rock bolt. The compositerock bolt consists of components such as a drill bit 1, a grouting pipe2, a main shaft 3, an anchor head assembly and an anchor tail assembly.The front end of the main shaft 3 is a threaded rod, the rear part ofthe drill bit 1 is provided with a threaded hole, and the drill bit 1 isin threaded connection with the front end of the main shaft 3. Theanchor head assembly includes a fixed ring 4, six pairs of drivenconnecting rods 501 and driving connecting rods 502, a limiting pipe 6and a sliding ring 7. The six pairs of driven connecting rods 501 anddriving connecting rods 502 are uniformly distributed along thecircumference. The fixed ring 4 is fixed at the front end of the mainshaft and is close to the rear part of the drill bit 1. The fixed ring 4and the driven connecting rods 501, the driven connecting rods 501 andthe driving connecting rods 502, and the driving connecting rods 502 andthe sliding ring 7 are all hinged. The sliding ring 7 is sleeved overthe main shaft 3; the limiting pipe 6 is located between the fixed ring4 and the sliding ring 7 and drilled some grouting holes on itsperiphery. The front part of the grouting pipe 2 is connected to thesliding ring by adopting pins; a sealing ring 8 is provided between thefront end of the grouting pipe and the sliding ring to seal the jointface.

As illustrated in FIG. 4, a foldable connecting rod unit is providedbetween adjacent driving connecting rods 502, and a grout stop screen 18is provided between each foldable connecting rod unit and the slidingring 7. As illustrated in FIGS. 5 and 6, the foldable connecting rodunit consists of two brace rods 16 and a ratchet box 17; the two bracerods are connected at one end by the ratchet box, and hinged at theother end to two adjacent driving connecting rods.

The anchor tail assembly includes an anchor plate 11, a connecting nut12 for closing the outer end of the grouting pipe, a spring 13, a nut 14and a locking ring 15. The anchor plate 11 is sleeved over the outerpart of the grouting pipe 2; the spring 13 is sleeved over theconnecting nut 12; the spring is compressed between the anchor plate 11and the nut 14, and the outer end of the nut 14 is provided with alocking ring 15 capable of preventing the nut from being loosened. Byrotating the nut 14 to enable the spring 13 to act on the anchor plate11, the rock bolt can be fastened.

According to the demand for the length of the rock bolt, each of thegrouting pipe 2 and the main shaft 3 may be integral, or may be formedby a plurality of sections connected by using connecting sleeves. Agrout stop plug 10 is sleeved over the outer part of the grouting pipe2. One grouting hole and one exhaust hole are drilled at two positionsof both the grout stop plug 10 and the anchor plate 11, and a groutinghole is also drilled in the connecting nut. When the driven connectingrods 501 are parallel to the main shaft 3, the inner sides of all drivenconnecting rods 501 are just in contact with the outer surface of thelimiting pipe 6, and the radius of the circle formed by hinging pointson the sliding ring 7 is smaller than the radius of the circle formed byhinging points on the fixed ring 4, thereby guaranteeing that threehinging points of each pair of driving connecting rod 502 and drivenconnecting rod 501 are always not co-linear, such that the drivingconnecting rods can smoothly push the driven connecting rods to enlargethe bolting hole around inner anchor end.

A method for anchoring the self-drilling differential grouting compositerock bolt includes the following steps:

As illustrated in FIG. 7, in step 1, hole drilling is performed. Thespring and nut of the composite rock bolt are removed, and a connectingnut is adjusted to make driven connecting rods to be parallel to a mainshaft. The composite rock bolt is driven by a bolter to rotate to drilla bolting hole till preset depth is reached.

As illustrated in FIG. 8, in step 2, hole expanding at the inner anchorend is performed. The connecting nut is gradually adjusted to enable agrouting pipe to push a sliding ring to the bottom of the hole such thatdriving connecting rods push the driven connecting rods to protrude inthe radial direction; at the same time, the rock bolt is driven by thebolter to rotate to enable the hole diameter of the inner anchor end tobe gradually expanded; the hole expanding of the inner anchor end iscompleted when the sliding ring is unable to move further to the bottomof the hole due to the block of the limiting pipe.

As illustrated in FIG. 9, in step 3, differential grouting is performed.First, the grouting pipeline is connected to the grouting hole of theconnecting nut; fracture grouting is performed to rocks around the inneranchor end through the internal part of the grouting pipe by adoptinghigh grouting pressure. Then, the grouting pipeline is connected to thegrouting hole of the anchor plate, and permeation grouting is performedto rocks around the grouting pipe through the gap between the groutingpipe and the bolting hole.

As illustrated in FIG. 10, in step 4, rock bolt fastening is performed.After grout is initially solidified, the spring and the locknut aremounted at the outer anchor end, and a certain pre-tightening force isapplied to the surrounding rock by using the locknut to compress thespring to produce a certain amount of compression.

The present invention is a reasonable combination of a drill bit, ananchor head assembly, a grouting pipe, a main shaft and an anchor tailassembly. It integrates the functions of drilling, differential groutingand rock bolting. The basic principle is as follows: the main shaft islocated in the grouting pipe and concentric and coaxial with thegrouting pipe; the inner anchor end of the rock bolt is provided withthe drill bit and the expandable anchor head assembly; the outer anchorend of the rock bolt is provided with the grout stop plug and the anchortail assembly; the inner anchoring point of the rock bolt is firm andreliable by virtue of the large-diameter anchor head assembly andfracture grouting; the connecting nut of the anchor tail assemblyensures the grouting pipe and the main shaft deforms in a coordinatedmanner; the spring not only enables the rock bolt to act in time and bein an active supporting state for a long time, but also has a certaincushioning and yielding effect. The grouting pipe anchors thesurrounding rock in a small range acting as a full-length anchorage; themain shaft compresses and reinforces the surrounding rock in a largerange; the grouting pipe anchorage zone and the main shaft anchoragezone interact with each other and cooperatively bear the load, such thatthe supporting performance can be effectively improved.

It should be pointed out that one skilled in the art may make variousimprovements and modifications without departing from the principle ofthe present invention, which, however, should be also considered as theprotection scope of the present invention.

1. A self-drilling differential grouting composite rock bolt, consistingessentially of a drill bit (1), a grouting pipe (2), a main shaft (3),an anchor head assembly and an anchor tail assembly, wherein the drillbit (1) is connected to the front end of the main shaft (3); thegrouting pipe (2) is sleeved over the main shaft (3), and the innerdiameter of the grouting pipe (2) is greater than the diameter of themain shaft (3), so a grouting passage is formed between the groutingpipe (2) and the main shaft (3); the anchor head assembly comprises asliding ring (7), a limiting pipe (6), and a plurality of pairs ofdriven connecting rods (501) and driving connecting rods (502); thesliding ring (7) is sleeved over the main shaft (3) and connected to thefront end of the grouting pipe (2); the limiting pipe (6) is sleevedover the main shaft (3) and located between the drill bit (1) and thesliding ring (7), and the limiting pipe (6) is provided with somegrouting holes; the length of the limiting pipe (6) is smaller than thetotal length of one pair of driving connecting rod and driven connectingrod; the driven connecting rods (501) are uniformly distributed alongthe circumferential direction and hinged to the front end of the mainshaft (3); the driving connecting rods (502) are uniformly distributedalong the circumferential direction and hinged to the sliding ring (7);the driven connecting rods (501) and the driving connecting rods (502)are hinged with each other; and the anchor tail assembly comprises ananchor plate (11) and a connecting nut (12); the anchor plate (11) issleeved over the rear end of the grouting pipe (2), and the connectingnut (12) is sleeved over the main shaft (3) and blocks the rear end ofthe grouting pipe (2); the connecting nut (12) is provided with agrouting hole connected with the grouting passage in the grouting pipe(2); the anchor plate is provided with a grouting hole and an exhausthole.
 2. The self-drilling differential grouting composite rock boltaccording to claim 1, wherein the anchor head assembly further comprisesa fixed ring (4), and the fixed ring (4) is fixed at the front part ofthe main shaft (3); each driven connecting rod (501) is hinged to thefixed ring (4), and the front end of the limiting pipe (6) is fixed tothe fixed ring (4).
 3. The self-drilling differential grouting compositerock bolt according to claim 1, wherein, when the driven connecting rods(501) are at a position parallel to the main shaft (3), the inner sideof each driven connecting rod (501) is in contact with the outer surfaceof the limiting pipe (6), and the radius of the circle formed by hingingpoints on the sliding ring is smaller than the radius of the circleformed by hinging points on the fixed ring.
 4. The self-drillingdifferential grouting composite rock bolt according to claim 1, whereina foldable connecting rod unit is provided between adjacent drivingconnecting rods, and a grout stop screen (18) is provided between eachfoldable connecting rod unit and the sliding ring.
 5. The self-drillingdifferential grouting composite rock bolt according to claim 4, whereinthe foldable connecting rod unit consists of two brace rods (16) and aratchet box (17), the two brace rods (16) are connected at one end bythe ratchet box (17), and hinged at the other end to two adjacentdriving connecting rods (502).
 6. The self-drilling differentialgrouting composite rock bolt according to claim 1, wherein the innerwall of the sliding ring (7) is provided with grooves in axialdirection, through which grout can enter the limiting pipe (6) from thegrouting pipe (2).
 7. The self-drilling differential grouting compositerock bolt according to claim 1, wherein a spring (13) is sleeved overthe connecting nut (12); next to the connecting nut (12) is a locknut(14) whose outer end is provided with a locking ring (15) capable ofpreventing the nut from being loosened.
 8. The self-drillingdifferential grouting composite rock bolt according to claim 1, whereina grout stop plug (10) is sleeved over the outer part of the groutingpipe (2); one grouting hole and one exhaust hole are drilled at twopositions of both the grout stop plug (10) and the anchor plate (11). 9.The self-drilling differential grouting composite rock bolt according toclaim 1, wherein each of the grouting pipe (2) and the main shaft (3) isintegral or is formed by a plurality of sections connected by usingconnecting sleeves.
 10. A method for anchoring the self-drillingdifferential grouting composite rock bolt of claim 1, comprising thefollowing steps: step 1: hole drilling removing the spring and nut ofthe self-drilling differential grouting composite rock bolt, adjusting aconnecting nut to make driven connecting rods to be parallel to a mainshaft, using a bolter to rotate the composite rock bolt to drill abolting hole with preset depth; step 2: hole expanding at inner anchorend adjusting the connecting nut gradually to enable a grouting pipe topush a sliding ring to the bottom of the hole such that drivingconnecting rods push the driven connecting rods to protrude in theradial direction, at the same time, using the bolter to rotate the rockbolt to enable the hole diameter of the inner anchor end to be graduallyexpanded, and completing the hole expanding process of the inner anchorend when the sliding ring is stopped by the limiting pipe; step 3:differential grouting connecting the grouting pipeline first with thegrouting hole of the connecting nut, performing fracture grouting torocks around the inner anchor end through the internal part of thegrouting pipe by adopting high grouting pressure, then connecting thegrouting pipeline with the grouting hole of the anchor plate, andperforming permeation grouting to rocks around the grouting pipe througha gap between the grouting pipe and the bolting hole; step 4: rock boltfastening mounting the spring and the locknut at the outer anchor endafter grout is initially solidified, and applying a certainpre-tightening force to the surrounding rock by using the locknut tocompress the spring to produce a certain amount of compression.
 11. Theself-drilling differential grouting composite rock bolt according toclaim 2, wherein, when the driven connecting rods (501) are at aposition parallel to the main shaft (3), the inner side of each drivenconnecting rod (501) is in contact with the outer surface of thelimiting pipe (6), and the radius of the circle formed by hinging pointson the sliding ring is smaller than the radius of the circle formed byhinging points on the fixed ring.